U.S. patent application number 10/326584 was filed with the patent office on 2003-06-26 for joint prostheses.
This patent application is currently assigned to Limber Ltd.. Invention is credited to Steinberg, Amiram.
Application Number | 20030120347 10/326584 |
Document ID | / |
Family ID | 26323126 |
Filed Date | 2003-06-26 |
United States Patent
Application |
20030120347 |
Kind Code |
A1 |
Steinberg, Amiram |
June 26, 2003 |
Joint prostheses
Abstract
A joint prosthesis comprising at least a first and a second load
carrying member, the first load carrying member being substantially
more shock absorbing and resilient than the second load carrying
member.
Inventors: |
Steinberg, Amiram; (Avihail,
IL) |
Correspondence
Address: |
DARBY & DARBY P.C.
Post Office Box 5257
New York
NY
10150-5257
US
|
Assignee: |
Limber Ltd.
|
Family ID: |
26323126 |
Appl. No.: |
10/326584 |
Filed: |
December 17, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10326584 |
Dec 17, 2002 |
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09902701 |
Sep 5, 2001 |
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09902701 |
Sep 5, 2001 |
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09043076 |
Feb 2, 1999 |
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09043076 |
Feb 2, 1999 |
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PCT/IL96/00098 |
Sep 4, 1996 |
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Current U.S.
Class: |
623/22.17 ;
623/17.13; 623/20.28; 623/22.26; 623/23.17; 623/23.41 |
Current CPC
Class: |
A61F 2002/30448
20130101; A61F 2002/30604 20130101; A61F 2002/30673 20130101; A61F
2/4609 20130101; A61F 2002/30599 20130101; A61F 2002/30594
20130101; A61F 2002/3412 20130101; A61F 2002/3631 20130101; A61F
2002/30369 20130101; A61F 2002/30642 20130101; A61F 2250/0018
20130101; A61F 2002/3007 20130101; A61F 2002/3208 20130101; A61F
2220/005 20130101; A61F 2310/00017 20130101; A61F 2220/0025
20130101; A61F 2002/30579 20130101; A61F 2002/30934 20130101; A61F
2002/3694 20130101; A61F 2250/0028 20130101; A61F 2002/30973
20130101; A61F 2/30749 20130101; A61F 2002/30662 20130101; A61F
2/30742 20130101; A61F 2002/30398 20130101; A61F 2002/3611
20130101; A61F 2230/0023 20130101; A61F 2002/30426 20130101; A61F
2002/30563 20130101; A61F 2210/0004 20130101; A61F 2230/0071
20130101; A61F 2002/3615 20130101; A61F 2002/30383 20130101; A61F
2002/30136 20130101; A61F 2002/30242 20130101; A61F 2002/30639
20130101; A61F 2002/3429 20130101; A61F 2002/30197 20130101; A61F
2002/30878 20130101; A61F 2002/30879 20130101; A61F 2/32 20130101;
A61F 2002/30652 20130101; A61F 2002/30354 20130101; A61F 2002/30795
20130101; A61F 2002/3652 20130101; A61F 2002/4635 20130101; A61F
2/38 20130101; A61F 2/36 20130101; A61F 2002/30777 20130101; A61F
2002/3082 20130101; A61F 2002/4619 20130101; A61F 2/08 20130101;
A61F 2/30965 20130101; A61F 2002/305 20130101; A61F 2002/3037
20130101; A61F 2/3601 20130101; A61F 2/3662 20130101; A61F
2002/30156 20130101; A61F 2002/30593 20130101; A61F 2230/0004
20130101; A61F 2002/30733 20130101; A61F 2220/0033 20130101; A61F
2002/30515 20130101; A61F 2002/30971 20130101; A61F 2220/0008
20130101; A61F 2/30767 20130101; A61F 2/44 20130101; A61F 2002/3613
20130101; A61F 2002/30009 20130101; A61F 2002/30014 20130101; A61F
2002/30062 20130101; A61F 2002/30581 20130101; A61F 2002/30919
20130101; A61F 2002/3216 20130101; A61F 2230/0045 20130101; A61F
2250/0063 20130101; A61F 2002/30574 20130101 |
Class at
Publication: |
623/22.17 ;
623/23.17; 623/22.26; 623/23.41; 623/17.13; 623/20.28 |
International
Class: |
A61F 002/32; A61F
002/30; A61F 002/38; A61F 002/44 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 4, 1995 |
IL |
115168 |
Claims
1. A hip joint prosthesis comprising an artificial femoral head
which is adapted to articulate with both a femur and an
acetabulum.
2. A hip joint prosthesis according to claim 1 and wherein said
artificial femoral head is constructed of a relatively rigid
material, compatible with human tissue.
3. A hip joint prosthesis according to claim 1 and wherein said
artificial femoral head is constructed of a material which is shock
absorbing.
4. A hip joint prosthesis according to claim 1 and wherein said
artificial femoral head is constructed of a material which is
resilient.
5. A hip joint prosthesis according to claim 1 and wherein said
artificial femoral head is generally spherical.
6. A hip joint prosthesis according to claim 1 and wherein said
artificial femoral head is formed with a hollow core.
7. A hip joint prosthesis according to claim 1 and also comprising
an artificial acetabulum having an articulating surface with which
said artificial femoral head articulates.
8. A hip joint prosthesis according to claim 1 and also comprising
an artificial femoral socket having an articulating surface with
which said artificial femoral head articulates, said artificial
femoral socket being adapted for fixed attachment to said
femur.
9. A hip joint prosthesis according to claim 2 and also comprising
an artificial femoral socket having an articulating surface with
which said artificial femoral head articulates, said artificial
femoral socket being adapted for fixed attachment to said
femur.
10. A hip joint prosthesis according to claim 1 and wherein said
artificial femoral head is formed with fluid passages adapted to
allow flow therethrough of synovial fluid.
11. A joint prosthesis comprising an artificial ball element which
is adapted to articulate with both first and second ball sockets
defined by a joint.
12. A joint prosthesis according to claim 11 and wherein said
artificial ball element is constructed of a relatively rigid
material, compatible with human tissue.
13. A joint prosthesis according to claim 11 and wherein said
artificial ball element is constructed of a material which is shock
absorbing.
14. A joint prosthesis according to claim 11 and wherein said
artificial ball element is constructed of a material which is
resilient.
15. A joint prosthesis according to claim 11 and wherein said
artificial ball element is generally spherical.
16. A joint prosthesis according to claim 11 and wherein said
artificial ball element is formed with a hollow core.
17. A joint prosthesis according to claim 11 and also comprising an
artificial ball socket having an articulating surface with which
said artificial ball element articulates.
18. A joint prosthesis according to claim 11 and also comprising an
artificial ball element socket having an articulating surface with
which said artificial ball element articulates, said artificial
ball element socket being adapted for fixed attachment to a
bone.
19. A joint prosthesis according to claim 12 and also comprising an
artificial ball element socket having an articulating surface with
which said artificial ball element articulates, said artificial
ball socket being adapted for fixed attachment to a bone.
20. A joint prosthesis according to claim II and wherein said
artificial ball element is formed with fluid passages adapted to
allow flow therethrough of synovial fluid.
Description
[0001] The present invention relates to apparatus and methods for
joint prosthesis surgery generally.
[0002] Joint prostheses are well known in the art. Generally joint
prostheses include a metal portion, typically constructed of steel
or titanium, which articulates with a bony portion of the body.
Non-articulating portions of the prosthesis are generally fixedly
attached to tissue or bone. For example, a hip joint prosthesis of
the art generally includes a metallic femoral head which
articulates with a portion of the hip bone, and a metallic stem
which is fixedly attached to the femur.
[0003] Several problems are associated with prostheses of the art,
for example, due to the mismatch between material properties of the
prosthesis and bone. The contact between metal and bone may cause
fretting wear of the bone. The difference in coefficient of thermal
expansion between metal and bone may cause discomfort to the
patient, especially during weather changes. The metallic prosthesis
provides virtually no shock absorption or damping.
[0004] It is known that a bone grows or regenerates according to
the stress which it must bear. The metal prosthesis generally bears
a much larger portion of weight than the surrounding bone. The
reduced stress on the surrounding bone may tend to contribute to
degeneration and recession of the bone, and to create an
undesirable gap between the bone and the prosthesis.
[0005] In order to overcome the aforementioned problems, a great
variety of prostheses with resilient portions have been proposed
and developed. The following U.S. patents are believed to be
representative of the art: U.S. Pat. Nos. 5,522,904, 5,514,184,
5,514,182, 5,507,836, 5,507,833, 5,507,830, 5,507,823, 5,507,820,
5,507,818, 5,507,814, 5,491,882, 5,489,311, 5,458,651, 5,458,643,
5,448,489, 5,425,779, 5,415,662, 5,405,411, 5,405,403, 5,389,107,
5,387,244, 5,376,125, 5,376,064, 5,370,699, 5,358,525, 5,344,459,
5,336,268, 5,330,534, 5,326,376, 5,316,550, 5,314,494, 5,314,493,
5,314,478, 5,290,314, 5,282,868, 5,222,985, 5,217,499, 5,217,498,
5,201,882, 5,201,881, 5,197,989, 5,197,987, 5,181,925, 5,171,276,
5,156,631, 5,151,521, 5,147,406, 5,146,933, 5,133,763, 5,116,374,
5,108,451, 5,108,446, 5,080,677, 5,049,393, 5,041,140, 5,019,107,
5,002,581, 4,997,447, 4,963,154, 4,963,153, 4,955,919, 4,955,912,
4,950,298, 4,938,773, 4,938,771, 4,936,856, 4,919,678, 4,919,674,
4,908,035, 4,904,269, 4,888,020, 4,822,365, 4,813,962, 4.808,186,
4,795,474, 4,795,470, 4,715,859, 4,664,668, 4,662,889, 4,661,112,
4,570,270, 4,344,193 and 3,875,594.
[0006] The present invention seeks to provide improved joint
prostheses which, inter alia, help overcome the above mentioned
problems of the prior art.
[0007] The prostheses provide shock absorption, damping and
resiliency. Portions of the prostheses which interface with human
tissue are preferably constructed of resilient materials which are
compatible with human bone or tissue, such as certain types of
polyurethane. Certain portions of the prostheses may be constructed
of composite materials whose mechanical or physical properties may
be optimized, such as to match properties of the local human bone
or tissue. By matching properties of the local bone or tissue, the
prosthesis behaves mechanically, structurally and thermally in a
manner similar to the local bone or tissue, which helps make the
prosthesis more efficient and comfortable.
[0008] An important feature of the prostheses is that they help
distribute stresses optimally, thereby stimulating regeneration of
bone.
[0009] The present invention is applicable for any joint in which
there is free movement, known in technical terms as a true
diarthrosis. True diarthroses include:
[0010] 1. Gliding joints, known as arthrodias, in which the
surfaces of the joint are flat, such as in the carpal bones;
[0011] 2. Hinge joints, known as ginglymi, such as the knee or
elbow;
[0012] 3. Condyloid joints, known as condylarthroses, which allow
flexion, extension and lateral movement, but no rotation, such as
the wrist, and saddle-shaped joints which allow the same type of
movement as condyloid joints, but are generally stronger, such as
the carpometacarpal joint of the thumb;
[0013] 4. Ball and socket joints, known as enarthroses, such as the
hip and the shoulder; and
[0014] 5. Pivot joints, known as trochoides, which only allow
rotation, such as the radio-ulnar joints.
[0015] The present invention will be described in detail
hereinbelow with respect to a prosthesis for an enarthrosis, such
as the hip joint, and to a prosthesis for a ginglymus, such as the
knee joint. It is appreciated, however, that a prosthesis for any
true diarthrosis is in the scope of the present invention.
[0016] In a radical departure from the prior art, and in accordance
with one embodiment of the present invention, a hip joint
prosthesis is provided which includes an artificial femoral head
which is not fixedly attached to the femur, but rather articulates
with both the femur and the acetabulum. The artificial femoral head
is generally spherical and may absorb shocks, provide damping
and/or be resilient. A separate, artificial femoral head is easier
to insert than the prostheses of the prior art which have a
stem.
[0017] In addition, the artificial femoral head may be provided
with delimiting rails or grooves which serve to define and limit
the movement paths of the femur with respect to the body, if
required, and dislocation of the joint is substantially prevented.
The delimiting rails or grooves may also serve as bumpers which
damp and cushion the femoral head at the limits of its
articulation.
[0018] The prostheses of the present invention may also be provided
with passageways for fluid, such as synovial fluid. Fluid present
in these passageways helps to lubricate the prosthesis and provides
viscous damping.
[0019] Since the prostheses of the present invention are resilient,
they geometrically adapt themselves to changes in static and
dynamic forces borne by the joint. In the case of the hip joint
prosthesis of the present invention, for example, normal raising of
the thigh does not apply substantial forces on the hip joint, and
the resilient hip joint prosthesis allows the freedom of movement
of a ball and socket joint with substantially no deformation nor
obstruction to movement due to friction between the prosthesis and
human tissue or bone, or between adjacent regions of the
prosthesis, such as between the artificial femoral head and an
artificial socket.
[0020] In contrast, when the person is standing, the static force
of the weight of the person on the hip joint causes the resilient
prosthesis to deform somewhat, i.e., to be squashed a certain
amount. This deformation provides a relatively larger area for
supporting the weight on the joint, thereby reducing pressure on
the joint. The deformation also increases the friction force
between the prosthesis and human tissue or bone, or between
adjacent regions of the prosthesis, such as between the artificial
femoral head and an artificial socket. The increased friction is
beneficial because it does not hinder the stationary person; on the
contrary, the increased friction increases stability of the
person.
[0021] The resiliency of the prosthesis is also beneficial during
sudden slips or falls. The dynamic and/or static forces due to the
sudden movement tend to deform or squash the resilient prosthesis.
As described above, the deformation reduces pressure on the joint,
reduces danger of the prosthesis detaching from the bone, and
increases friction which helps provide stability during the slip or
fall.
[0022] There is thus provided in accordance with a preferred
embodiment of the present invention, a joint prosthesis including
at least a first and a second load carrying member, the first load
carrying member being substantially more shock absorbing and
resilient than the second load carrying member.
[0023] In accordance with a preferred embodiment of the present
invention, at least one of the load carrying members is
characterized in having at least one of strength and elasticity
generally similar to that of human cartilage.
[0024] There is also provided in accordance with a preferred
embodiment of the present invention, a joint prosthesis including a
plurality of alternating adjacent portions of substantially rigid
and substantially resilient materials.
[0025] There is also provided in accordance with a preferred
embodiment of the present invention, a joint prosthesis including a
plurality of alternating adjacent first and second portions, the
first portion having a substantially rigid configuration and the
second portion having a substantially resilient configuration.
[0026] Preferably at least one of the first and the second portions
is generally omega shaped. The joint prosthesis may include at
least one portion compatible with human tissue. The joint
prosthesis may have at least one hollow portion.
[0027] Preferably, any of the joint prostheses includes at least
one delimiting rail or groove.
[0028] Preferably, any of the joint prostheses includes at least
one passageway for a fluid.
[0029] There is also provided in accordance with a preferred
embodiment of the present invention, a hip joint prosthesis
including an artificial, spherical femoral head which is adapted to
articulate with an acetabulum and an upper portion of a thigh.
[0030] There is also provided in accordance with a preferred
embodiment of the present invention, a hip joint prosthesis
including an artificial, self-articulating femoral head, the head
being attachable to at least one of an acetabulum and an upper
portion of a thigh.
[0031] Preferably, the hip joint prosthesis includes an artificial
femoral head which is shock absorbing, provides damping and/or is
substantially resilient.
[0032] Preferably, the femoral head has at least one hollow
portion.
[0033] Further in accordance with a preferred embodiment of the
present invention, the hip joint prosthesis also includes an
artificial acetabulum attachable to an innominate bone, the
artificial femoral head articulating with the artificial
acetabulum.
[0034] Still further in accordance with a preferred embodiment of
the present invention, the hip joint prosthesis also includes an
artificial femoral socket attachable to a femur, the artificial
femoral head articulating with the artificial femoral socket.
[0035] Further in accordance with a preferred embodiment of the
present invention, the artificial femoral head includes a device
for substantially preventing dislocation of the artificial femoral
head from the artificial acetabulum, the artificial femoral socket,
or both.
[0036] Preferably the device for substantially preventing
dislocation is shock absorbing or resilient.
[0037] Further in accordance with a preferred embodiment of the
present invention, the artificial femoral head includes at least
one delimiting rail or groove. The delimiting groove may have a
different geometrical shape than that of the rail. This permits
providing various predetermined ranges and paths of motion.
[0038] Still further in accordance with a preferred embodiment of
the present invention, the artificial femoral head has at least one
passageway for a fluid.
[0039] Additionally in accordance with a preferred embodiment of
the present invention, the hip joint prosthesis includes a sleeve
which envelops at least one portion of the prosthesis and which is
attachable to at least one of a portion of an innominate bone and a
thigh. Preferably the sleeve includes a relatively high strength
fabric.
[0040] Further in accordance with a preferred embodiment of the
present invention, the artificial femoral socket is adapted to fit
substantially snugly with at least one upper portion of a
femur.
[0041] Still further in accordance with a preferred embodiment of
the present invention, the artificial femoral head includes a
plurality of alternating adjacent portions of substantially rigid
and substantially resilient materials.
[0042] Additionally in accordance with a preferred embodiment of
the present invention, the hip joint prosthesis further includes a
stem insertable into a femur.
[0043] Further in accordance with a preferred embodiment of the
present invention, the hip joint prosthesis includes an outer layer
attachable to a femur, the outer layer including a material
compatible with human tissue.
[0044] There is also provided in accordance with a preferred
embodiment of the present invention, a knee joint prosthesis
including a femoral portion and a tibial portion, the femoral
portion being attachable to a femur and the tibial portion being
attachable to a tibia, the femoral portion articulating with the
tibial portion, wherein at least one of the femoral portion and the
tibial portion is shock absorbing, provides damping or is
substantially resilient.
[0045] In accordance with a preferred embodiment of the present
invention, the knee joint prosthesis includes a device operative to
limit motion of the tibia with respect to the femur.
[0046] Preferably, the device operative to limit motion of the
tibia with respect to the femur, is shock absorbing.
[0047] Additionally in accordance with a preferred embodiment of
the present invention, the femoral portion is generally convex and
the tibial portion is generally concave.
[0048] Alternatively in accordance with a preferred embodiment of
the present invention, the femoral portion is generally convex and
the tibial portion is generally convex.
[0049] Further in accordance with a preferred embodiment of the
present invention, the knee joint prosthesis includes at least one
roller element, the femoral portion articulating with the tibial
portion via the at least one roller element.
[0050] Preferably, the knee joint prosthesis has at least one fluid
passageway.
[0051] There is also provided in accordance with a preferred
embodiment of the present invention, a bone fastener including a
plurality of alternating adjacent portions of substantially rigid
and substantially resilient materials.
[0052] There is also provided in accordance with a preferred
embodiment of the present invention, a bone fastener, including a
plurality of alternating adjacent first and second portions, the
first portion having a substantially rigid configuration and the
second portion having a substantially resilient configuration.
[0053] There is also provided in accordance with a preferred
embodiment of the present invention, a method of incision of a
ligament including forming a substantially wave-like incision in
the ligament.
[0054] There is also provided in accordance with a preferred
embodiment of the present invention, a method of insertion of a hip
joint prosthesis including:
[0055] fixedly attaching a first joint element to an upper portion
of a femur, the first joint element fitting substantially snugly
with the upper portion of the femur;
[0056] fixedly attaching a second joint element to a portion of an
innominate bone; and
[0057] inserting an artificial femoral head intermediate the first
and the second joint elements, such that the artificial femoral
head articulates with at least one of the first and the second
joint elements.
[0058] Preferably, one or more natural or artificial ligaments may
be used to strengthen the hip joint.
[0059] There is also provided in accordance with a preferred
embodiment of the present invention, a method for limiting a range
of movement of a hip joint including:
[0060] implanting a hip joint prosthesis comprising at least one
delimiting rail and at least one delimiting groove, the at least
one delimiting rail articulating with the at least one delimiting
groove, such that the at least one delimiting groove limits
articulation of the at least one delimiting rail therein.
[0061] The present invention will be understood and appreciated
from the following detailed description, taken in conjunction with
the drawings in which:
[0062] FIG. 1 is a simplified illustration of a human hip
joint;
[0063] FIG. 2 is a simplified illustration of a hip joint
prosthesis, constructed and operative in accordance with a
preferred embodiment of the present invention;
[0064] FIG. 3 is a partially sectional illustration of the hip
joint prosthesis of FIG. 2;
[0065] FIG. 4 is a partially sectional illustration of the hip
joint prosthesis of FIG. 2, wherein the femur is rotated
laterally;
[0066] FIG. 5 is a partially sectional illustration of the hip
joint prosthesis of FIG. 2, wherein the femur is rotated
rearwardly;
[0067] FIG. 6 is a simplified pictorial illustration of an
artificial femoral head of the hip joint prosthesis of FIG. 2, the
femoral head comprising two delimiting rails;
[0068] FIGS. 7A and 7B are simplified illustrations of an
artificial femoral head, constructed and operative in accordance
with another preferred embodiment of the present invention,
articulating with artificial and natural acetabula respectively,
and wherein the artificial femoral head has no delimiting
rails;
[0069] FIGS. 8A and 8B are simplified illustrations of an
artificial femoral head fixedly attached to a stem, constructed and
operative in accordance with yet another preferred embodiment of
the present invention, articulating with artificial and natural
acetabula respectively, and wherein the artificial femoral head has
no delimiting rails;
[0070] FIG. 8C is a simplified illustration of an artificial,
self-articulating femoral head fixedly attached to a stem and to an
acetabulum, constructed and operative in accordance with a
preferred embodiment of the present invention;
[0071] FIG. 9A is a simplified pictorial illustration of an
artificial femoral head and an artificial acetabulum, constructed
and operative in accordance with still another preferred embodiment
of the present invention, and wherein the artificial femoral head
has one delimiting rail which articulates with the generally
elliptically shaped acetabulum;
[0072] FIG. 9B is a simplified sectional illustration of the
femoral head of FIG. 9A, taken along lines 9B-9B in FIG. 9A;
[0073] FIG. 9C is a simplified pictorial illustration of a flexible
and stable bone connector, constructed and operative in accordance
with a preferred embodiment of the present invention;
[0074] FIGS. 9D and 9E are simplified, sectional illustrations of a
flexible and stable bone connector stem of a hip joint prosthesis,
constructed and operative in accordance with a preferred embodiment
of the present invention, before and after deployment,
respectively;
[0075] FIGS. 9F and 9G are simplified, sectional illustrations of a
flexible and stable bone connector stem of a hip joint prosthesis,
constructed and operative in accordance with another preferred
embodiment of the present invention, before and after deployment,
respectively;
[0076] FIG. 10 is a simplified sectional illustration of a
non-hollow artificial femoral head, constructed and operative in
accordance with a preferred embodiment of the present
invention;
[0077] FIG. 11 is a simplified sectional illustration of an
artificial femoral head, constructed and operative in accordance
with another preferred embodiment of the present invention, and
wherein the femoral head comprises a plurality of hollow
portions;
[0078] FIG. 12 is a simplified sectional illustration of an
artificial femoral head, constructed and operative in accordance
with yet another preferred embodiment of the present invention, and
wherein the femoral head comprises a plurality of hollow portions
filled with a fluid;
[0079] FIG. 13 is a simplified sectional illustration of an
artificial femoral head, constructed and operative in accordance
with still another preferred embodiment of the present invention,
and wherein the femoral head comprises a plurality of portions,
each portion not necessarily having the same mechanical or physical
properties;
[0080] FIG. 14A is a simplified sectional illustration of an
artificial femoral head, constructed and operative in accordance
with another preferred embodiment of the present invention, and
wherein the femoral head comprises a protruding delimiting
bumper;
[0081] FIG. 14B is a simplified sectional illustration of an
artificial femoral head, constructed and operative in accordance
with yet another preferred embodiment of the present invention, and
wherein the femoral head comprises a thin, resilient outer shell
and a resilient core;
[0082] FIG. 15 is a simplified pictorial illustration of an
artificial femoral head, constructed and operative in accordance
with a preferred embodiment of the present invention, and including
delimiting grooves;
[0083] FIG. 16 is a simplified sectional illustration of an
artificial femoral head, constructed and operative in accordance
with another preferred embodiment of the present invention, and
wherein the femoral head has fluid passageways;
[0084] FIG. 17 is a simplified sectional illustration of an
artificial femoral head, constructed and operative in accordance
with yet another preferred embodiment of the present invention;
[0085] FIGS. 18A and 18B are simplified pictorial and sectional
illustrations respectively of an artificial femoral head,
constructed and operative in accordance with another preferred
embodiment of the present invention, and wherein the femoral head
comprises a plurality of alternating adjacent portions of
substantially rigid and substantially resilient materials, FIG. 18B
being taken along lines 18B-18B in FIG. 18A;
[0086] FIGS. 18C-18F are simplified pictorial illustrations of
alternative constructions of a femoral head including a plurality
of alternating adjacent portions of substantially rigid and
substantially resilient materials;
[0087] FIG. 18G is a simplified pictorial illustration of an
artificial acetabulum, constructed and operative in accordance with
a preferred embodiment of the present invention;
[0088] FIGS. 18H, 18I and 18J are simplified illustrations of
installing the artificial acetabulum of FIG. 18G into a natural
acetabulum, in accordance with a preferred embodiment of the
present invention;
[0089] FIGS. 18K and 18L are simplified sectional illustrations of
two artificial acetabula, constructed and operative in accordance
with two preferred embodiments of the present invention;
[0090] FIGS. 19A-19C are simplified pictorial illustrations of a
method of incision of ligaments, such as prior to insertion of a
hip joint prosthesis, in accordance with a preferred embodiment of
the present invention;
[0091] FIG. 20 is a simplified pictorial illustration of a sleeve
for joining a femoral head with the innominate bone, constructed
and operative in accordance with a preferred embodiment of the
present invention;
[0092] FIG. 21 is a simplified sectional illustration of an
expandable artificial femoral head, constructed and operative in
accordance with a preferred embodiment of the present
invention;
[0093] FIG. 22 is a simplified illustration of a human knee
joint;
[0094] FIGS. 23 and 24 are respective simplified side and front
view illustrations of a knee joint prosthesis, constructed and
operative in accordance with a preferred embodiment of the present
invention;
[0095] FIG. 25 is a simplified illustration of a femoral portion of
the knee joint prosthesis of FIGS. 23 and 24;
[0096] FIG. 26 is a simplified illustration of a tibial portion of
the knee joint prosthesis of FIGS. 23 and 24;
[0097] FIGS. 27 and 28 are respective simplified side and front
view illustrations of a knee joint prosthesis, constructed and
operative in accordance with another preferred embodiment of the
present invention;
[0098] FIGS. 29 and 30 are respective simplified side and front
view illustrations of a knee joint prosthesis, constructed and
operative in accordance with yet another preferred embodiment of
the present invention;
[0099] FIGS. 31 and 32 are respective simplified side and front
view illustrations of a knee joint prosthesis, constructed and
operative in accordance with still another preferred embodiment of
the present invention;
[0100] FIG. 33 is a simplified illustration of a roller element
included in the knee joint prosthesis of FIGS. 31 and 32;
[0101] FIG. 34 is a simplified, partially sectional illustration of
a bone fastener, constructed and operative in accordance with a
preferred embodiment of the present invention; and
[0102] FIG. 35 is a simplified, partially sectional illustration of
a vertebra replacement, constructed and operative in accordance
with a preferred embodiment of the present invention.
[0103] The present invention will now be described in detail with
respect to a prosthesis for an enarthrosis, an example being the
hip joint, and to a prosthesis for a ginglymus, an example being
the knee joint. It is appreciated, however, that a prosthesis for
any true diarthrosis is in the scope of the present invention.
[0104] For a better understanding of a hip joint prosthesis, a
basic description of the human hip joint is presented here with
reference to FIG. 1, which illustrates the hip of the right side of
the body. The hip joint is a ball and socket joint, the ball being
the femoral head (head of the thigh bone) which articulates with
the acetabulum of the innominate bone, known in non-technical terms
as the socket of the hip bone.
[0105] The innominate bone in the area of the hip joint is made of
three portions: the upper portion is called the ilium, the middle
portion is called the pubis and the lower portion is called the
ischium. The femoral head is connected to the innominate bone by a
plurality of ligaments. The ligaments shown in FIG. 1 are the
iliofemoral ligaments and the pubo-femoral ligament. There is also
an ischio-femoral ligament, not seen in FIG. 1. The femoral head
articulates with a fibrous rim of the acetabulum called the
cotyloid ligament.
[0106] Generally a hip joint replacement of the prior art involves
replacing the natural femoral head with a metallic artificial
femoral head which is fixedly attached to a stem. The stem is
generally inserted in the femur and the femoral head articulates
with the acetabulum, if still intact, or some other depression,
artificial or natural, in the innominate bone. Some or all of the
ilio-femoral, pubo-femoral and ischio-femoral ligaments may be
removed to provide access to the femoral head and acetabulum.
[0107] Reference is now made to FIGS. 2 and 3 which illustrate a
hip joint prosthesis 10, constructed and operative in accordance
with a preferred embodiment of the present invention. In a radical
departure from the prior art, hip joint prosthesis 10 comprises a
femoral head 12 which is not fixedly attached to the femur, but
rather is capable of articulating with both the thigh and the
innominate bone. In accordance with a preferred embodiment of the
present invention, femoral head 12 may be constructed of a rigid
material compatible with human tissue, for example, a metal such as
stainless steel, or a structural plastic.
[0108] In accordance with another preferred embodiment of the
present invention, artificial femoral head 12 is constructed of a
material which is shock absorbing, and additionally or
alternatively provides damping, and additionally or alternatively
is resilient. An example of such a material is polyurethane or
synthetic rubber.
[0109] A resilient artificial femoral head, unlike the prior art,
yields upon application of forces and substantially returns to its
original shape after such forces are removed.
[0110] Artificial femoral head 12 is preferably, although not
necessarily, generally spherical in shape. In accordance with a
preferred embodiment of the present invention, and as shown in FIG.
3, femoral head 12 has a hollow core 14. Hollow core 14, inter
alia, adds to the resiliency and shock absorbing characteristics of
femoral head 12.
[0111] In accordance with a preferred embodiment of the present
invention, hip joint prosthesis 10 also comprises an artificial
acetabulum 16 which is preferably fixedly attached to the
innominate bone via an acetabulum interface 18. Artificial femoral
head 12 articulates with artificial acetabulum 16.
[0112] Additionally in accordance with a preferred embodiment of
the present invention, hip joint prosthesis 10 comprises an
artificial femoral socket 20 which is preferably fixedly attached
to the femur via a stem 22. Alternatively, socket 20 may be
attached to the femur without a stem, for example, by bonding.
Artificial femoral head 12 articulates with artificial femoral
socket 20. Socket 20 is shaped to facilitate this articulation,
such as being generally concave. In addition, socket 20 is
preferably shaped to overlap, or snugly fit, the upper portion of
the natural femur. The generally concave, overlapping shape of
artificial femoral socket 20 helps distribute stresses optimally on
the femur, thereby stimulating regeneration of bone.
[0113] Socket 20 may overlap and "hug" the upper portion of the
femur on the outside surface of the femur. Alternatively or
additionally, socket 20 may be configured to fit snugly into an
inner surface of the femur.
[0114] It is important to note that socket 20 serves two general
tasks, as described above. The first task is articulation with
artificial femoral head 12. The second task is fitting snugly with
the femur and distributing stresses evenly thereon.
[0115] It is appreciated that in accordance with another preferred
embodiment of the present invention, socket 20 may comprise two
separate portions each generally dedicated to serving one of the
above described tasks. A first portion 20A, generally concave in
shape, may be generally dedicated to articulation with artificial
femoral head 12. A second portion 20B, generally shaped as a
"crown" to hug and snugly fit circumferentially around and on top
of the femur, may be generally dedicated to distributing stresses
evenly on the femur. This is true of any of the sockets described
herein with reference to any of the embodiments of the present
invention. The "crown", i.e., second portion 20B, greatly changes
the loading conditions of prosthesis 10, decreases stresses exerted
on the femur by stem 22, and creates a new and healthier stress
distribution on the surrounding bone and tissue. With the support
of second portion 20B, stem 22 may have a much smaller section
throughout and particularly at its neck.
[0116] Stem 22 preferably includes a core 24 and an outer layer 26,
as seen in FIGS. 2 and 3. Outer layer 26 preferably includes one or
more ridges 28, which, inter alia, help distribute stresses and
help fasten stem 22 to the femur.
[0117] Core 24 of stem 22, artificial acetabulum 16 and artificial
femoral socket 20 are preferably constructed of a rigid material,
for example, stainless steel or a structural plastic.
Alternatively, the rigid material may be a composite material, such
as a lay-up of graphite fibers, which may be constructed to have
mechanical or physical properties, such as modulus of elasticity or
coefficient of thermal expansion, equivalent to that of the local
human bone.
[0118] Stem 22 provides excellent three-dimensional anchorage to
the bone, and induces three-dimensional loading stress conditions
as close as possible to the natural conditions. The improved stress
field distribution at the interface between the prosthesis and the
bone helps prevent lysis. The stress field set up by the prosthesis
inside the bone helps induce regeneration and strengthening of the
bone.
[0119] Acetabulum interface 18 and outer layer 26 of stem 22 are
preferably made of a resilient material compatible with human
tissue, such as polyurethane, which helps distribute stresses
optimally, thereby stimulating regeneration of bone. In accordance
with a preferred embodiment of the present-invention, acetabulum
interface 18 and outer layer 26 of stem 22 are constructed of a
material, such as polyurethane, which has one or more mechanical
and/or physical properties substantially similar to human
cartilage.
[0120] Hip joint prosthesis 10 may include a device for
facilitating removal as is known in the art, such as a threaded
boss or hole (both not shown).
[0121] It may sometimes be desired to limit the number of degrees
of freedom of the hip joint or the range of a particular degree of
freedom of movement of the femur with respect to the acetabulum,
depending on the needs of the patient. It may also be desired to
provide safeguards to substantially prevent dislocation of the
joint. In accordance with a preferred embodiment of the present
invention, apparatus is provided to achieve these goals, as is now
described.
[0122] Reference is now made additionally to FIGS. 4-6. In
accordance with a preferred embodiment of the present invention,
artificial femoral head 12 is provided with an upper delimiting
rail 30 and a lower delimiting rail 32. Upper delimiting rail 30
slides in a channel 34 in artificial acetabulum 16. Channel 34 is
oriented generally forwards and rearwards with respect to the human
body. As seen in FIG. 5, upper delimiting rail 30 slides forwards
in channel 34 when the femur is moved backwards. It is appreciated
that upper delimiting rail 30 slides backwards in channel 34 when
the femur is moved forwards.
[0123] Lower rail 32 slides in a channel 36 in artificial femoral
socket 20. As seen in FIG. 4, as the femur is moved laterally away
from the body, lower rail 32 slides in channel 36 of socket 20 and
butts thereagainst. Upper delimiting rail 30 is similarly
constrained to slide in channel 34. Constraining the travel of
rails 30 and 32 in channels 34 and 36, respectively, substantially
prevents overtravel of the femur and substantially prevents
dislocation of artificial femoral head 12 from artificial
acetabulum 16 and artificial femoral socket 20. Moreover, since
femoral head 12 is preferably constructed of a shock absorbing or
resilient material, the butting of rails 30 and 32 against channels
34 and 36, respectively, is substantially cushioned and damped.
[0124] Variations of hip joint prosthesis 10 are possible within
the scope of the present invention. Reference is now made to FIGS.
7A and 7B which illustrate an artificial femoral head 40,
constructed and operative in accordance with another preferred
embodiment of the present invention. Artificial femoral head 40 may
be similar in construction and operation to artificial femoral head
12 of FIGS. 2-6. Femoral head 40 differs from femoral head 12 in
that femoral head 40 has no delimiting rails. In FIG. 7A, femoral
head 40 is shown articulating with an artificial acetabulum 42. In
FIG. 7B, femoral head 40 is shown articulating with a natural
acetabulum 44.
[0125] Reference is now made to FIGS. 8A and 8B which illustrate an
artificial femoral head 46 fixedly attached to a crown 48,
constructed and operative in accordance with yet another preferred
embodiment of the present invention. Femoral head 46 and crown 48
may be constructed of a resilient material, such as
polyurethane.
[0126] Crown 48 may be attached to an upper portion of the thigh.
Alternatively, as shown in FIG. 8A, crown 48 may be attached to a
stem 49. Stem 49 may include a core 49A and an outer layer 49B.
Core 49A may be of solid construction, and additionally or
alternatively, may include at least one hollow portion. Outer layer
49B may be constructed of a material with properties similar to
human cartilage.
[0127] In FIG. 8A, femoral head 46 articulates with an artificial
acetabulum 50. Femoral head 46 may have an upper delimiting rail
(not shown) which articulates with a corresponding groove (not
shown) in artificial acetabulum 50. Alternatively, femoral head 46
may have a delimiting groove with which articulates a corresponding
rail in artificial acetabulum 50.
[0128] In FIG. 8B, femoral head 46 articulates with a natural
acetabulum 52. Femoral head 46 may include a hollow portion (not
shown), as described hereinabove for artificial femoral head 12
with respect to FIGS. 2-6.
[0129] Alternatively, in accordance with another preferred
embodiment of the present invention, artificial femoral head 46 may
be fixedly attached to artificial acetabulum 50. In such an
embodiment, artificial femoral head 46 may articulate with crown
48.
[0130] Reference is now made to FIG. 8C which illustrates an
artificial, self-articulating femoral head 55 fixedly attached to a
stem 56 and to an artificial acetabulum 57, constructed and
operative in accordance with a preferred embodiment of the present
invention. Femoral head 55 is preferably constructed of a resilient
material, such as polyurethane. Artificial acetabulum 57 may have
any suitable shape, typically being generally shell-shaped or
spherical.
[0131] Articulation of the thigh with the innominate bone is not
achieved by articulation of femoral head 55 with artificial
acetabulum 57, but rather is achieved by the self-articulation of
femoral head 55. "Self-articulation" is defined as the ability of
femoral head 55 to permit rotary and translatory motion of the
thigh with respect to the innominate bone due to the resilient and
elastic properties and configuration of femoral head 55. Stem 56
may comprise an outer layer 58 which may have properties similar to
human cartilage.
[0132] Reference is now made to FIGS. 9A and 9B which illustrate an
artificial femoral head 60 and an artificial acetabulum 62,
constructed and operative in accordance with still another
preferred embodiment of the present invention. Artificial femoral
head 60 has one delimiting rail 64 which articulates with a
generally elliptically shaped recess 66 in artificial acetabulum
62. It is appreciated that this type of rail may be employed in any
of the other artificial femoral heads described herein, either as
an upper rail or a lower rail or both.
[0133] Artificial femoral head 60 may be provided with one or more
fluid passageways 67, as seen in FIG. 9A, for flow therethrough of
a fluid (not shown), such as synovial fluid. It is appreciated that
any of the artificial femoral heads of the present invention may be
provided with fluid passageways. Fluid passageways 67 help
lubricate artificial femoral head 60, and provide damping.
[0134] Reference is now made to FIG. 9C which illustrates a
flexible and stable bone connector 450, constructed and operative
in accordance with a preferred embodiment of the present invention.
Connector 450 preferably includes a hollow, generally tubular
portion 452 and a bone interface portion 454. Interface portion 454
is preferably shaped to snugly fit the inner geometry of the bone
into which it is placed. The inner geometry of the bone may be
determined by such methods as a computer tomography, and interface
portion 454 may then be machined accordingly.
[0135] In accordance with a preferred embodiment of the present
invention, interface portion 454 has a fluted shape with a
plurality of protruding fins 456. The fluted shape of interface
portion 454 and the hollowness of tubular portion 452 promote bone
development and growth after implanting the prosthesis. Connector
450 may be fashioned in a variety of configurations, such as
straight, curved, cylindrical or tapered, for example.
[0136] A known problem associated with the repair of broken bones
and with the insertion of stems of femoral prostheses into femurs,
is that the bone may have a curvature which changes along the
length thereof in three dimensions. It is difficult to match the
curvature of the stem of the prosthesis to the natural curvature of
the bone. In practice, usually a set of standardized connecting
pins or prostheses are used and the closest matching prosthesis is
selected and further machined or filed in the operating theater to
match the measured natural curvature of the femur. Even with this
method, gaps are almost inevitable between the prosthesis and the
inner bone tissue.
[0137] It is a particular feature of the present invention that
connector 450 is sufficiently flexible so that it can be inserted
into a bored portion of the bone, such as a femur, and deform to
adapt to the changing curvature of the bone, thereby helping to
solve the aforementioned problem. Connector 450 is preferably
constructed of a material which provides flexibility to permit
insertion into the bone, while at the same time providing
sufficient structural stability once connector 450 is in place. A
suitable material is one having a non-linear, "half-bell-shaped"
stress-strain relationship, for example, a plastic such as
polyurethane. The material may be reinforced with fibers, whose
density and orientation may be selected in accordance with a
particular engineering requirement.
[0138] Reference is now made to FIGS. 9D and 9E which illustrate a
flexible and stable bone connector stem 460 of a hip joint
prosthesis, constructed and operative in accordance with a
preferred embodiment of the present invention. Stem 460 may be
readily employed in any of the femoral prostheses of the present
invention.
[0139] Stem 460 is preferably constructed similarly to connector
450, and preferably includes a fluted elongated portion 462 having
a hollow portion 464 and a plurality of protruding fins 466. A
force transfer element 468, such as a wire, rod or cable, with a
plurality of bulges 470 is preferably disposed in hollow portion
464. Element 468 may be made of any suitable stiff, biocompatible
material, such as DYNEEMA.
[0140] Stem 460 is preferably inserted into the femur in the
orientation shown in FIG. 9D. After insertion, element 468 is then
moved generally in the direction of an arrow 472, thereby causing
bulges 470 to deform fluted portion 462, as seen in FIG. 9D, and
fix stem 460 firmly in the femur.
[0141] Reference is now made to FIGS. 9F and 9G which illustrate a
flexible and stable bone connector stem 480 of a hip joint
prosthesis, constructed and operative in accordance with another
preferred embodiment of the present invention. Stem 480 may also be
readily employed in any of the femoral prostheses of the present
invention.
[0142] Stem 480 preferably includes a fluted elongated portion 482
in which is disposed a sleeve 484 having a plurality of bulges 486.
Disposed inside sleeve 484 is hollow shaft 488. Sleeve 484 is
arranged for sliding, axial motion with respect to fluted portion
482 and shaft 488.
[0143] As describe hereinabove for fluted portion 462, fluted
portion 482 is sufficiently flexible so that it can be inserted
into a bored portion of a femur and deform to adapt to the changing
curvature of the femur.
[0144] Stem 480 is preferably inserted into the femur in the
orientation shown in FIG. 9F. After insertion, sleeve 484 is then
moved generally in the direction of an arrow 490, thereby causing
bulges 486 to deform fluted portion 482, as seen in FIG. 9D, and
fix stem 480 firmly in the femur.
[0145] Artificial femoral head 12 shown in FIGS. 2-6, has a hollow
core 14. Reference is now made to FIG. 10 which illustrates a
non-hollow artificial femoral head 70, constructed and operative in
accordance with a preferred embodiment of the present invention.
Artificial femoral head 70 may include an upper rail 72 and a lower
rail 74.
[0146] Reference is now made to FIG. 11 which illustrates an
artificial femoral head 80, constructed and operative in accordance
with another preferred embodiment of the present invention. Femoral
head 80 comprises a plurality of hollow portions 82.
[0147] Reference is now made to FIG. 12 which illustrates an
artificial femoral head 90, constructed and operative in accordance
with yet another preferred embodiment of the present invention.
Femoral head 90 comprises a plurality of hollow portions 92 filled
with a fluid, such as synovial fluid. Additionally or
alternatively, one or more fluid passageways 94 may be provided.
The fluid in portions 92 or passageways 94 may enhance the shock
absorbing and damping characteristics of femoral head 90.
[0148] Reference is now made to FIG. 13 which illustrates an
artificial femoral head 100, constructed and operative in
accordance with still another preferred embodiment of the present
invention. Femoral head 100 comprises a plurality of portions 102,
each portion 102 not necessarily having the same mechanical or
physical properties. Portions 102 may be used to enhance, to
optimize or to customize the shock absorbing and damping
characteristics of femoral head 100.
[0149] Reference is now made to FIG. 14A which illustrates an
artificial femoral head 110, constructed and operative in
accordance with another preferred embodiment of the present
invention. Femoral head 110 comprises a protruding delimiting
bumper 112 instead of a delimiting rail.
[0150] Reference is now made to FIG. 14B which illustrates an
artificial femoral head 113, constructed and operative in
accordance with yet another preferred embodiment of the present
invention. Femoral head 113 comprises a thin, resilient outer shell
114 and a resilient core 115. Shell 114 may be constructed of
DYNEEMA high performance polyethylene fibers, commercially
available from DSM, Netherlands. DYNEEMA, particularly in the form
of a woven fabric, provides a combination of high strength with
excellent shock absorbing and damping characteristics, as well as
being biocompatible. Core 115 may also be made of DYNEEMA with
properties engineered to meet requirements such as strength or
resilience, for example, and may be impregnated with other
materials, such as a resin.
[0151] Reference is now made to FIG. 15 which illustrates an
artificial femoral head 120, constructed and operative in
accordance with a preferred embodiment of the present invention.
Femoral head 120 includes delimiting grooves 122 which articulate
with corresponding rails (not shown) in an artificial acetabulum
and an artificial socket (not shown).
[0152] Reference is now made to FIG. 16 which illustrates an
artificial femoral head 130, constructed and operative in
accordance with another preferred embodiment of the present
invention. Femoral head 130 has fluid passageways 132 which allow
flow therethrough of a fluid, preferably synovial fluid, the
natural lubrication fluid of the human body. Fluid passageways 132
may be configured in a variety of orientations, configurations and
sizes. Alternatively or additionally, passageways 132 may be
provided in an artificial femoral socket 134 or an artificial
acetabulum 136.
[0153] Fluid flowing in fluid passageways 132 may help lubricate
femoral head 130. The presence of fluid in fluid passageways 132
may also enhance the shock absorbing and damping characteristics of
femoral head 130.
[0154] As mentioned above, the ligaments connecting the femur and
the innominate bone may be removed in the prior art, before
placement of a hip joint prosthesis. This is unfortunate because
these ligaments are amongst the strongest ligaments in the body.
These ligaments strengthen the joint and help prevent dislocation.
Preserving some or all of the ligaments is therefore desirable.
[0155] Reference is now made to FIG. 17 which illustrates an
artificial femoral head 140, constructed and operative in
accordance with yet another preferred embodiment of the present
invention. Artificial femoral head 140 is preferably relatively
small in size, thereby helping to reduce the need for tampering
with some of the hip joint ligaments. In this embodiment, femoral
head 140 articulates with an artificial acetabulum 142 and an
artificial socket 144. Socket 144 may be attached directly to the
femur without a stem, such as by bonding or via a crown (not shown)
similar to the crown-shaped portion 20B described hereinabove with
reference to FIGS. 2 and 3.
[0156] By eliminating the stem, the need for tampering with or
drilling into the femur may also be eliminated. There may be no
need to remove the entire natural femoral head, but rather a
portion thereof may be preserved. Preserving part of the femur may
simplify the surgical operation and may preserve most of the
strength of the bone.
[0157] The need for tampering with some of the ligaments may also
be reduced. Indeed, the intact ligaments themselves act together
with the prosthesis of FIG. 17, because they tend to keep femoral
head 140 properly installed. In addition, the embodiment of FIG. 17
may be more easily and quickly implanted than prostheses having
stems.
[0158] Other embodiments of the present invention which address the
problem of preserving the hip joint ligaments are described
hereinbelow with respect to FIGS. 19A-21.
[0159] Reference is now made to FIGS. 18A and 18B which illustrate
an artificial femoral head 150, constructed and operative in
accordance with another preferred embodiment of the present
invention. Femoral head 150 comprises a plurality of alternating
adjacent portions 152 and 154 of substantially rigid and
substantially resilient materials respectively. The rigid material
is preferably a composite material and the resilient material is
preferably polyurethane. In accordance with a preferred embodiment
of the present invention, femoral head 150 is attached to an
artificial acetabulum 156.
[0160] The material composition and the geometry of the portions
152 and 154 may be optimized to provide the desired rigidity and
resiliency. In this manner, femoral head 150 may be constructed as
a non-linear spring with multiple spring constants.
[0161] Femoral head 150 may have different rigidity and resiliency
for forward-backward motion as opposed to lateral motion. For
example, as seen in FIG. 18B, adjacent portions 152 and 154 are
generally omega-shaped. Such a shape permits relatively easy
swinging of the femur forwards and backwards with respect to the
body, while at the same time constraining the swinging range to
prevent overtravel of the femur. The resiliency of femoral head 150
damps the motion of the femur at the limits of its swing. The omega
shape is stiffer in the lateral direction, thus limiting lateral
motion of the femur with respect to the body. It is appreciated
that femoral head 150 may be alternatively constructed to allow
greater freedom of motion laterally than forwards and
backwards.
[0162] Reference is now made to FIGS. 18C and 18D which show
femoral heads 160 and 162 respectively, with adjacent layers 161
and 163 of substantially rigid and substantially resilient
materials, respectively, constructed and operative in accordance
with an alternative preferred embodiment of the present invention.
As shown in FIGS. 18E and 18F, femoral heads 160 and 162 may be
provided with apertures 164 and 166 respectively, which may, for
example, provide a passageway for synovial fluid, nerves, blood
vessels, ligaments, tissues, elongated force transmitting members
or prosthetic controls. Fluid in apertures 164 and 166 may enhance
the damping of femoral heads 160 and 162 respectively.
[0163] It is appreciated that the embodiments of FIGS. 18A-18F may
be used as hinge or joint elements in other applications where it
is desired to provide different rigidity or resiliency in different
directions of motion.
[0164] Reference is now made to FIG. 18C which illustrates an
artificial acetabulum 400, constructed and operative in accordance
with a preferred embodiment of the present invention.
[0165] Artificial acetabulum 400 preferably includes an interface
402 made of a resilient, cartilage-like material, and preferably
has a generally triangular cutout 404. Acetabulum 400 preferably
also includes an outer ridge 406 that "snap-fits" into the natural
acetabulum socket, thereby substantially fixing artificial
acetabulum 400 in the natural socket. The natural acetabulum may
have to be drilled, cut or otherwise machined to ensure a proper
snap fit so that acetabulum 400 is rigidly held in place. Ridge 406
may be continuous or may be formed of discrete portions that
protrude into the natural acetabulum recesses. As seen in FIG. 18G,
interface 402 may comprise a deformable, resilient flange 408 with
expandable, accordion-like folds. Interface 402 may be one highly
deformable piece, or may be slightly deformable, in which case it
may fit into the natural acetabulum with a slight "click".
[0166] It is a particular feature of the present invention that
ridge 406 provides shock absorption and positively locks interface
402 into a recess prepared in the natural socket, without any need
for screws or adhesive. Interface 402 may comprise one or more
layers. The large surface area of interface 402 provides a large
load bearing and shock absorbing surface for a femoral head.
Interface 402 may itself serve as an articulating surface for a
femoral head, in which case the large surface area diminishes
fretting and wearing of the articulating surfaces.
[0167] Reference is now made to FIGS. 18K and 18L which illustrate
a cross section of interface 402 constructed in accordance with two
preferred embodiments of the present invention. In FIG. 18K, it is
seen that interface 402 preferably includes a plurality of
protrusions 410 for locking interface 402 in recesses prepared in
the natural socket. As seen in FIGS. 18G and 18L, interface 402 may
also include an "umbilical" protrusion 412 that is configured to
fit the natural or restructured "umbilical" recess of the natural
acetabulum. This allows reduction of machining of the innominate
bone and leaves a stronger bone.
[0168] Acetabulum 400 also preferably includes a locking piece 414
complementary shaped and sized to snugly fit into triangular
cut-out 404. Interface 402 together with locking piece 414 may be
used as the articulating portion of the prosthesis with the femur.
Additionally, there is preferably provided an articulation portion
416 which snaps together with a recess 418 formed in interface 402.
Articulation portion 416 may be made of metal, composite material,
cartilage-like material, polyurethane or DYNEEMA. Articulation
portion 416 may alternatively be attached to interface 402 by means
of a bayonet type of connection or simply a press fit without
clicking. Articulating portion 416 makes artificial acetabulum 400
into one stable integral assembly which is easily assembled in and
removed from the innominate bone.
[0169] Reference is now made to FIGS. 18H, 18I and 18J which
illustrate installing artificial acetabulum 400 into a natural
acetabulum, in accordance with a preferred embodiment of the
present invention. In FIG. 18H, an insertion tool 420 squeezes
triangular cut-out 404 inwardly in the direction of arrows 422, to
allow insertion of interface 402 into the natural socket. Upon
release of insertion tool 420, cut-out 404 springs outwards much in
the manner of a retaining ring, thereby pressing interface 402
firmly against and into the natural socket. Prongs of the insertion
tool may be placed in prepared recesses or holes in interface
402.
[0170] In FIG. 18I, locking piece 414 is inserted into cut-out 404,
thereby completing the shape of acetabulum 400 and firmly locking
interface 402 into the natural socket when an articulating head or
an additional articulating surface is assembled therewith. In FIG.
18J, articulation portion 416 is snapped together with interface
402, thereby making artificial acetabulum 400 into one integral
assembly.
[0171] As mentioned above, the ligaments connecting the femur and
the innominate bone may be removed in the prior art, before
placement of a hip joint prosthesis. Methods for preserving the hip
joint ligaments, or reinforcing or replacing them, are now
described.
[0172] Reference is now made to FIGS. 19A-19C which illustrate a
method of incision of ligaments, such as prior to insertion of a
hip joint prosthesis, in accordance with a preferred embodiment of
the present invention. A primary goal of the method of incision is
to preserve the ligaments.
[0173] FIG. 19A illustrates a hip joint 170 prior to incision. As
seen in FIG. 19B, a wave-like incision 172 may be made, such as
with a laser device, in any or all of the ilio-femoral,
pubo-femoral and ischio-femoral ligaments. As seen in FIG. 19C, the
cut ligaments allow ample room for placement of a hip joint
prosthesis (not shown).
[0174] As is known in the art, ligaments generally contract after
incision, impairing mending of the ligament tissue. The wave-like
shape of incision 172 permits slightly shifting the ligaments so
that there is sufficient contact or overlap of the ligaments even
after contraction, thereby helping to promote stitching and mending
of the ligament tissue.
[0175] Reference is now made to FIG. 20 which illustrates a sleeve
180 for joining a femoral head 182 with the innominate bone,
constructed and operative in accordance with a preferred embodiment
of the present invention. Sleeve 180 is preferably made of a high
strength woven fabric, such as DYNEEMA, polyethylene, nylon or
polyurethane. Sleeve 180 preferably comprises filaments with a high
elasticity modulus in the longitudinal direction of the ligaments,
along an axis 184, and a circumferential stretching weave along an
axis 186, generally perpendicular to axis 184, as seen in FIG.
20.
[0176] Sleeve 180 also preferably includes an anchoring band 188
for attaching sleeve 180 to the innominate bone. Anchoring band 188
may be attached to the innominate bone and sleeve 180 may be
attached to the femoral head by any suitable means, such as bonding
or with mechanical fasteners. Sleeve 180 may replace or assist the
natural ligaments of the hip joint. Sleeve 180 may also help in
mending of ligament tissue after surgery. All or portions of sleeve
180 may be constructed of a material, such as material used for
dissolving sutures, which eventually dissolves after a
predetermined period.
[0177] The present invention also provides a hip joint prosthesis
which may substantially reduce the need for tampering with the hip
joint ligaments. Reference is now made to FIG. 21 which illustrates
an expandable artificial femoral head 190, constructed and
operative in accordance with a preferred embodiment of the present
invention. Femoral head 190 is preferably constructed of a
resilient material, such as polyurethane. When expanded, femoral
head 190 has substantially the same shape as femoral head 12,
described hereinabove with reference to FIGS. 2 and 3.
[0178] In contrast to the prior art, femoral head 190, before
expansion, may be inserted between the existing ligaments with
minimum tampering thereof. Femoral head 190 may then be expanded to
the desired shape. Femoral head 190 may be inflated by means of a
fluid (not shown) introduced, for example, via a thin needle valve
(not shown). Alternatively, femoral head 190 may be expanded by
introducing therein components of an expandable foam (not shown),
which expand inside femoral head 190.
[0179] The present invention will now be described in detail with
respect to a prosthesis for a ginglymus, namely the knee joint. For
a better understanding of a knee joint prosthesis, a basic
description of the human knee joint is presented here with
reference to FIG. 22, which illustrates the knee of the right
leg.
[0180] The knee is a hinge comprising the internal and external
condyles of the femur which articulate with the upper end of the
tibia. The femoral condyles are separated by a deep fossa. The
upper end of the tibia comprises two tuberosities, the external of
which articulates with the head of the fibula.
[0181] The knee also comprises the trochlea of the femur (not shown
in FIG. 22) which is located forward and upward of the condyles.
The patella slides along the trochlea. The patella is shown pulled
down in FIG. 22 in order to show some of the ligaments and
cartilage which connect the femur, tibia, fibula and patella. These
ligaments and cartilage include, inter alia, the external lateral
ligament which connects the external femoral condyle to the fibula,
the internal lateral ligament which connects the internal femoral
condyle to the tibia, the ligamentum patellae to which is attached
the patella, and the transverse ligament and internal semilunar
cartilage which are attached to the head of the tibia. The
transverse ligament, internal semilunar cartilage and the anterior
crucial ligament are attached to the spine (not shown in FIG. 22)
of the tibia. The spine is a series of elevations on the head of
the tibia opposite the fossa between the femoral condyles.
[0182] Reference is now made to FIGS. 23 and 24 which illustrate a
knee prosthesis 200, constructed and operative in accordance with a
preferred embodiment of the present invention. Knee prosthesis 200
comprises an upper or femoral portion 202 and a lower or tibial
portion 204, as seen in FIGS. 23 and 24.
[0183] Referring additionally to FIG. 25, it is seen that femoral
portion 202 preferably comprises two pads 206 upon which rest the
internal and external condyles of the femur, as seen in FIG. 24,
and a trochlear portion 208 which is intermediate the patella and
the trochlea, as seen in FIG. 23. Pads 206 articulate with tibial
portion 204. As seen in FIG. 25, femoral portion 202 also
preferably has a socket 210, whose function is described
hereinbelow with reference to tibial portion 204.
[0184] Referring additionally to FIG. 26, it is seen that tibial
portion 204 includes an artificial spine 212 which extends into
socket 210. It is appreciated that when the knee flexes, socket 210
restricts the movement of spine 212 therein. Socket 210 and/or
spine 212 are preferably constructed of a shock absorbing or
resilient material, such that the movement of spine 212 is
cushioned at the limits of travel in socket 210.
[0185] As seen in FIG. 23, spine 212 may extend beyond socket 210
into the fossa of the femur. Tibial portion 204 also preferably has
two depressions 214 with which pads 206 may articulate. Tibial
portion 204 preferably includes a stem 216 for attachment to the
tibia. Tibial portion 204 may have one or more hollow portions 218
to increase shock absorption, damping or resiliency.
[0186] As seen in FIG. 23, a tibial cushion 220 may be placed
intermediate tibial portion 204 and the head of the tibia, tibial
cushion 220 preferably being constructed of a material compatible
with human tissue, such as polyurethane. In accordance with a
preferred embodiment of the present invention, femoral portion 202
may be constructed of a substantially rigid material, such as a
composite material, and tibial portion 204 may be constructed of a
substantially resilient material, such as polyurethane.
[0187] In accordance with another preferred embodiment of the
present invention, femoral portion 202 may be constructed of a
substantially resilient material and tibial portion 204 may be
constructed of a substantially rigid material.
[0188] In accordance with yet another preferred embodiment of the
present invention, femoral portion 202 may be constructed of a
substantially resilient material and tibial portion 204 may be
constructed of a substantially resilient material.
[0189] It is appreciated that knee prosthesis 200 is operative to
absorb static and dynamic shocks.
[0190] It is a particular feature of the present invention that the
resiliency of either femoral portion 202 or tibial portion 204
allows the configuration of the contact surfaces between portions
202 and 204 to change according to physical factors, such as load
or motion. For example, when bearing loads directed downwards on
the tibia, the contact area between portions 202 and 204 becomes
relatively large, thereby increasing stability and decreasing
pressure on the tibia. When the knee flexes, the contact area is
relatively small, which facilitates motion of the tibia with
respect to the femur. Femoral portion 202 and tibial portion 204
have different radii of curvature when not exposed to forces. The
radii of curvature approach equality when bearing forces directed
downwards on the tibia.
[0191] Reference is now made to FIGS. 27 and 28 which illustrate a
knee prosthesis 230, constructed and operative in accordance with
another preferred embodiment of the present invention. Knee
prosthesis 230 comprises an upper or femoral portion 232 and a
lower or tibial portion 234, as seen in FIGS. 27 and 28. Tibial
portion 234 is substantially identical to tibial portion 204
described hereinabove with reference to FIGS. 23, 24 and 26.
[0192] Femoral portion 232 preferably comprises two pads 236 upon
which rest the internal and external condyles of the femur, as seen
in FIG. 28, and a trochlear portion 238 which is intermediate the
patella and the trochlea, as seen in FIG. 27. Pads 236 articulate
with tibial portion 234. Pads 236 preferably have one or more
hollow portions 240, and may have one or more fluid passageways
242, for permitting flow therethrough of synovial fluid, thereby
providing lubrication and enhancing the shock absorbing and damping
characteristics of knee prosthesis 230.
[0193] Femoral portion 232 articulates with tibial portion 234 of
knee prosthesis 230 by sliding along the generally concave surface
of tibial portion 234. Reference is now made to FIGS. 29 and 30
which illustrate a knee prosthesis 250, constructed and operative
in accordance with another preferred embodiment of the present
invention. Knee prosthesis 250 comprises an upper or femoral
portion 252 and a lower or tibial portion 254, as seen in FIGS. 29
and 30. Femoral portion 252 is preferably generally convex and
articulates with tibial portion 254 by rolling along the generally
convex surface of tibial portion 254.
[0194] As described hereinabove with reference to FIG. 23, the
resiliency of either femoral portion 252 or tibial portion 254
allows the configuration of the contact surfaces between portions
252 and 254 to change according to physical factors, such as load
or motion.
[0195] Reference is now made to FIGS. 31 and 32 which illustrate a
knee prosthesis 260, constructed and operative in accordance with
another preferred embodiment of the present invention. Knee
prosthesis 260 comprises an upper or femoral portion 262 which
articulates with a lower or tibial portion 264 by means of one or
more roller elements 266, as seen in FIGS. 31 and 32.
[0196] Portions 262 and 264 may be substantially rigid and roller
elements 266 may be substantially resilient. Conversely, portions
262 and 264 may be substantially resilient and roller elements 266
may be substantially rigid.
[0197] Roller elements 266 may permit articulation of femoral
portion 262 with tibial portion 264 by means of rolling, sliding, a
combination of rolling and sliding, or rolling combined with a
deformation of one or more of roller elements 266. Roller elements
266 may be formed in any shape which provides such rolling and
sliding, such as being generally cylindrical in shape. An
alternative shape is shown in FIG. 33.
[0198] At least one fluid passageway 268 may be provided in each
roller element 266 for passage therethrough of a fluid, such as
synovial fluid, thereby providing lubrication and enhancing the
shock absorbing and damping characteristics of knee joint
prosthesis 260.
[0199] Alternatively or additionally, each roller element 266 may
have at least one hollow portion. Alternatively or additionally,
each roller element 266 may comprise a plurality of portions, each
portion not necessarily having the same mechanical or physical
properties. These portions may be used to enhance, to optimize or
to customize the shock absorbing and damping characteristics of the
roller element 266.
[0200] Femoral portion 262 may be attached directly to the femoral
condyles. Alternatively, as shown in FIG. 32, a femoral pad 270 may
be placed intermediate femoral portion 262 and the femoral
condyles. Femoral pad 270 may be constructed of a material with
properties similar to human cartilage, such as polyurethane.
[0201] Reference is now made to FIG. 34 which illustrates a bone
fastener 300 for fastening bone fractures, constructed and
operative in accordance with a preferred embodiment of the present
invention.
[0202] Bone fastener 300 preferably includes a core 302 and an
outer layer 304. Outer layer 304 preferably includes one or more
ridges 306, which, inter alia, help distribute stresses and help
fasten bone fastener 300 to a bone. Core 302 may be of solid or
hollow construction. Bone fastener 300 may have any suitable cross
sectional shape, such as circular or elliptical.
[0203] In accordance with a preferred embodiment of the present
invention, core 302 is preferably constructed of a rigid material,
for example, stainless steel or a structural plastic.
Alternatively, the rigid material may be a composite material, such
as graphite fibers, which may be constructed to have mechanical or
physical properties, such as modulus of elasticity or coefficient
of thermal expansion, equivalent to that of the local human
bone.
[0204] Outer layer 304 is preferably made of a resilient material
compatible with human tissue, such as polyurethane, which helps
distribute stresses optimally, thereby stimulating regeneration of
bone. In accordance with a preferred embodiment of the present
invention, outer layer 304 is constructed of a material, such as
polyurethane, which has one or more mechanical and/or physical
properties substantially similar to human cartilage.
[0205] Reference is now made to FIG. 35 which illustrates a
vertebra replacement 310, constructed and operative in accordance
with a preferred embodiment of the present invention.
[0206] Vertebra replacement 310 preferably includes at least one
inner member 312, at least one intermediate member 314 and at least
one outer member 316. Inner member 312 is preferably constructed of
a substantially resilient material and may have one or more hollow
portions 318. Alternatively, portions 318 may be filled with a
fluid, such as synovial fluid. Additionally or alternatively, a
fluid passageway (not shown) may be provided for fluid flow
therethrough, thereby providing lubrication and enhancing the shock
absorbing and damping characteristics of vertebra replacement
310.
[0207] Intermediate portion 314 may be less flexible than inner
member 312, and is preferably constructed of a rigid material, for
example, stainless steel or a structural plastic. Alternatively,
the rigid material may be a composite material, such as graphite
fibers, which may be constructed to have mechanical or physical
properties, such as modulus of elasticity or coefficient of thermal
expansion, equivalent to that of the local human bone.
[0208] Outer members 314 are preferably made of a resilient
material compatible with human tissue, such as polyurethane, which
helps distribute stresses optimally. In accordance with a preferred
embodiment of the present invention, outer members 314 may be
constructed of a material, such as polyurethane, which has one or
more mechanical and/or physical properties substantially similar to
human cartilage.
[0209] In accordance with a preferred embodiment of the present
invention, geometrical data may be provided, such as by
computerized tomography, and be used to prepare and select an
optimal prosthesis or bone fastener prior to surgery. Data input,
such as from the results of computerized tomography, may be used to
match the geometry of the prosthesis or bone fastener to the needs
of the patient. Either the prosthesis or the bone, or both, may be
shaped, such as by computerized machining, using the geometrical
data obtained.
[0210] Alternatively, the geometry of a preformed, standard
prosthesis may be used to reshape the bone to match the prosthesis.
Alternatively, the geometrical data used to reshape the bone may be
used generally to form the prosthesis in real time.
[0211] It is appreciated that various features of the invention
which are, for clarity, described in the contexts of separate
embodiments may also be provided in combination in a single
embodiment. Conversely, various features of the invention which
are, for brevity, described in the context of a single embodiment
may also be provided separately or in any suitable
subcombination.
[0212] It will be appreciated by persons skilled in the art that
the present invention is not limited to what has been particularly
shown and described hereinabove. Rather, the scope of the present
invention is defined only by the claims that follow:
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